This invention relates to a window member to be used in an optical device such as a system employing ultraviolet light, visible radiation, infrared radiation, or X-rays.
The optical window member of this invention comprises a diamond film reinforced with a lattice-like substrate. To obtain this window member, there is employed a manufacturing method which comprises forming a diamond film on a substrate and etching the central part of the substrate in a lattice-like pattern by a photolithographic technique. This method allows an addition to the surface area of the window member and a reduction in the cost thereof and enhances the compression strength thereof.
As widely known, diamond excels in perviousness to light in a wide range extending from the ultraviolet region of about 0.3 .mu.m in wavelength to the far infrared region of about 25 .mu.m in wavelength and, because of its configuration of carbon atoms of a small atomic number, preeminently excels in perviousness to X-rays. It further exhibits high heatproofness up to about 1,200.degree. C. in vacuum and up to about 600.degree. C. in the air. Thus, it is expected to find extensive utility as optical window members.
Conventional manufacture of an optical window made of diamond involves preparing from a raw material of natural or synthetic diamond a disk several mm in diameter and mechanically grinding the diamond disc to a sufficient thinness. However, since diamond crystals of large diameters occur rarely and are extremely expensive, it is very difficult to produce an optical window made of diamond with a large surface area (at least 1 cm in diameter, for example). Moreover, the manufacture by grinding entails a disadvantage in that the work of machining is extremely expensive because diamond is the hardest of all substances.